Idaho's Wild Singletrack Spa

Mountain biking and soaking in a hot springs go together like a wink and a smile. Throw in a bit of fly-fishing, and you've got a wink, a smile, and the perfect pickup line for the adventure-minded traveler. The new Idaho Hot Springs Mountain Bike Route, from the Adventure Cycling Association, traces a 500-mile route through the Sawtooth National Forest, which encompasses 50 accessible hot springs and a whole lot of trees and rock slides. It's a unique adventure that has bikers pedaling forest roads and singletrack toward commercial hot springs and remote, primitive pools – which just so happen to sit next to some of the West's most storied fly-fishing streams.

"It's not possible to do this kind of tour anywhere else in the U.S.," says Casey Greene, the cartographer who mapped the route for the ACA. "Idaho has the most soakable hot springs in the country. And the rivers and singletrack are phenomenal. Nowhere else comes close."

Pedaling the whole route is a two-week adventure, but you can drop your gear in Ketchum and spend a weekend riding the singletrack that surrounds Sun Valley, hitting front country hot springs like Frenchman's Bend. Or use the more rugged Stanley as your home base and systematically knock out the singletrack and hot springs within the Sawtooth National Recreation Area. Kem Hot Springs, for example, sits on the bank of the Salmon River, offering perfect 110-degree soaking in a rock pool.

Regardless of where you hang your hat, there are a few things everyone has to do on this trip. You have to ride the 18-mile Fisher Creek/Williams Creek loop, which boasts one of the best cross-country descents in the Northern Rockies. You have to get a beer and a burger at the Powerhouse bike shop in Hailey (yes, it's a bike shop with a grill and bar). And you have to drop a line in the Big Wood River. Visiting Ernest Hemingway's grave in Ketchum wouldn't be a bad idea either.

More information: Summer and fall are the best seasons for riding. Fly into Boise, and rent a bike at Elephant's Perch in Ketchum. A number of guide services in the area offer guided multiday trips if you don't want to go it alone. Western Spirit is the industry standard in fully supported bike trips.